Resolve DTLS cookie and version before session resumption.

Session resumption involves a version check, so version negotiation must
happen first. Currently, the DTLS implementation cannot do session
resumption in DTLS 1.0 because the ssl_version check always checks
against 1.2.

Switching the order also removes the need to fixup ssl_version in DTLS
version negotiation.

Signed-off-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Viktor Dukhovni <viktor@openssl.org>

RT: #4392, MR: #2452